Rare fossilized embryos, believed to be more than 500 million years old, have been unearthed by researchers at the University of Missouri.
Fossilized records from the Cambrian Period, which occurred between 540 million and 485 million years ago, provide glimpses into evolutionary biology when the world's ecosystems rapidly changed and diversified.
Most fossils show the organisms' skeletal structure, which may or may not give researchers accurate pictures of these prehistoric organisms.
James Schiffbauer from MU explained that before the Ediacaran and Cambrian Periods, organisms were unicellular and simple.
The Cambrian Period ushered in the advent of shells and over time shells and exoskeletons can be fossilized, giving scientists clues into how organisms existed millions of years ago, he said.
Schiffbauer and his team, including doctoral student Jesse Broce, collected fossils from the lower Cambrian Shuijingtuo Formation in the Hubei Province of South China and analyzed samples to determine the chemical makeup of the rocks.
Soft tissue fossils have different chemical patterns than harder, skeletal remains, helping researchers identify the processes that contributed to their preservation.
It is important to understand how the fossils were preserved, because their chemical makeups can also offer clues about the nature of the organisms' original tissues, Schiffbauer said.
Schiffbauer said that something obviously went wrong in these fossils because Earth has a pretty good way of cleaning up after things die and here, the cells' self-destructive mechanisms didn't happen, and these soft tissues could be preserved.
While studying the fossils, they found over 140 spherically shaped fossils, some of which include features that are reminiscent of division stage embryos, essentially frozen in time, he said.
The fossilized embryos the researchers found were significantly smaller than other fossil embryos from the same time period, suggesting they represent a yet undescribed organism.
The study is published in the Journal of Paleontology.